This invention relates to a flow meter and, in particular but not exclusively, to a flow meter for milk.
Flow meters for determining the flow rate of fluids are known. However, these are typically mechanical arrangements or incorporate mechanical mechanisms which can lead to inaccuracies and failure over time.
Further problems occur when trying to determine the flow rate of milk, since the specific gravity and viscosity of milk varies throughout milking, from cow to cow, and depends on the time of year due to, for example, entrained air, butterfat content, and mastitis.
The entrained air and surface tension of milk can vary considerably. Foaming can occur due to vacuum creation in the lines transporting the milk, and with the formation of slugs. It is desirable to separate or reduce the air from the milk so that volumetric measurements can be made under calm or relatively calm flow conditions.
Furthermore, the conductive and dielectric properties of milk may not only vary from cow to cow, but also may vary during the milking cycle. The constituents of milk exhibit varying impedances when subjected to alternating and direct currents (AC and DC). Milk cannot therefore be measured reliably by measuring bulk conductivity and may, under turbulent flow conditions, appear to become inductive.
The present invention seeks to provide a solution to these problems.
According to the present invention, there is provided a flow meter comprising an inflow chamber having a first fluid inlet, an outflow chamber housed in the inflow chamber and having a second fluid inlet, which is in fluid communication with the inflow chamber, and a fluid outlet by which fluid can drain from the outflow chamber, and a sensing device having an elongate sensor which is positioned at, or adjacent to and downstream of, the second fluid inlet, the second fluid inlet being of limited dimensions so that, in use, a head of fluid is formed in the inflow chamber and the flow rate of the fluid passing through the second fluid inlet is monitored based on the extent of the elongate sensor which is covered by the fluid.